From drunken student toga parties to the 12 million annual visitors to the Colosseum – the might of ancient Rome has echoed down the centuries in all sorts of unexpected ways. Roman buildings, technologies, words and ideas still permeate our world, while gold-helmeted gladiators, purple-robed emperors and arrow-straight Roman roads remain almost as iconic as they were in the 1st century AD. Rome's cultural legacy is so large that its language, Latin, is still sometimes taught in schools, even though it's not been spoken for well over a millennium.

Click through this gallery to see how much you really know about ancient Rome – and fill in the gaps...

The Roman Empire is rightly heralded as perhaps the most influential empire in history, but for area it doesn’t even break the top 20. Clustered around the Mediterranean, it stretched from Portugal in the west to Iraq in the east and from Sudan in the south to Scotland in the north – reaching 1.9 million square miles (5 million sq km) in AD 117. It's a big number, but it would be comfortably outstripped by Mongol khanates, Arab caliphates and the many European empires of the 19th century. Rome wasn’t even the largest dominion of its day, lagging several million square miles behind the Han Empire in ancient China, and was roughly half the size of the modern United States.

Today Rome is synonymous with laurel-wreathed Caesars imperiously commanding slaves, soldiers and senators alike. But for its first 500 years Rome was a republic – a democracy (of sorts) that ruled through a series of elected assemblies. Indeed, Julius Caesar, today Rome’s most famous figure, was never emperor. Dominating the dying days of the Roman Republic, he was a senator, quaestor, aedile, praetor, tribune, consul and briefly ‘dictator-for-life’ – but never emperor. The office of emperor was both invented by and first occupied by his great-nephew Augustus in 27 BC – 17 years after Caesar’s brutal murder.

A compelling creation myth was a must for every ancient civilisation, but Rome decided that one just wasn’t enough. In myth number one, brothers Romulus and Remus are raised by a she-wolf before going to war over the location of their new city – a story still known around the world today. In myth number two, Trojan hero Aeneas founds the city after fleeing the destruction of Troy – a narrative pushed by Roman poet Virgil in his magnum opus, The Aeneid. Both these stories were well-known in Roman times, and some writers even tried – with little success – to synthesise them into a single coherent narrative.

When exactly Rome fell is one of history's eternal questions. By the 5th century AD the empire was split into a western half centred on Rome and an eastern half centred on Constantinople (modern-day Istanbul). The city of Rome fell in AD 410, sacked for the first time in 800 years by an army of marauding Goths. The Western Roman Empire stumbled on for a few more decades, and was finally blotted out in AD 476. But the Eastern Roman Empire lived on for another millennium – until Constantinople fell to the Turks in 1453. A few fringe scholars even argue that Rome fell in 1806 with the demise of the Holy Roman Empire, a Christian confederation that took its authority from the Pope – in Rome.

It's perhaps the most famous ancient building on Earth, but if you asked a 2nd-century-AD Roman the way to the Colosseum they wouldn't have known where you meant. The building we now call the Colosseum opened with 100 days of games in AD 80 under the Latin name Amphitheatrum Flavium ('the Flavian Amphitheatre'), named for its sponsors in the ruling Flavian dynasty who had taken the imperial throne a decade earlier. The shorthand 'the Colosseum' dates from the Middle Ages, by which time the building was already a crumbling ruin.

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At its peak the Roman army comprised almost half a million men – that's more than the modern-day armies of Britain and France combined. Size mattered in ancient warfare, but the Romans also had the best armour, the best weapons and the best training, and the crack battalions that invaded Britain in AD 43 defeated armies 10 times their size. A typical Roman attack involved soldiers approaching enemy lines in formation, hurling short spears called pilums and then charging, with a back line providing extra projectile support. If needed, they could adopt a 'tortoise' formation (pictured), a moving shield wall designed to withstand enemy arrow fire.

For all Rome's might, no military is invincible. In 216 BC, Carthaginian general Hannibal marched his elephants over the Alps and obliterated the Romans at the Battle of Cannae, almost ending Rome's story there and then. In 53 BC, Roman plutocrat Crassus invaded Parthia with seven legions of heavy infantry, which were promptly wiped out by fast-moving horse archers and desert heat. Crassus's head was cut off and used as a prop in a play for the Parthian king. And in AD 7, three legions met their end in the mud of the Teutoburg Forest after an ambush by Germanic tribes. The emperor Augustus was so devastated that he paced his palace, howling at the Gods to "give me back my legions".

From Michelangelo's David to the columns of the US Capitol, for centuries now artists and architects have used plain white marble to imitate the timeless elegance of the classical world. Which is profoundly ironic, because even the sternest Roman statues were once painted all the colours of the rainbow – the pigments have simply faded in the intervening millennia. This image shows a famous statue of Rome's first emperor Augustus alongside a replica decorated with its likely original colour scheme. It doesn't look quite so refined, does it?

The Romans didn’t actually invent a lot of the things they’re famous for – sewers, roads, the alphabet and aqueducts were all advanced by the Romans rather than created – but none can doubt their claim to the hypocaust, an efficient form of underfloor heating. A furnace heats an open space below a floor supported by stacks of bricks, warming both tiles and feet. They also pioneered an extremely durable and water-resistant brand of concrete, which has helped their temples and bathhouses stand for millennia and counting. It's not a coincidence that the Colosseum is still a proud part of Rome's skyline, while many more recent monuments have crumbled to dust.

Julius Caesar has lent his name to the month of July, the British battleship HMS Caesar and the amanita caesarea species of mushroom – but not, incidentally, the Caesar salad, which was named after Italian chef Caesar Cardini. Perhaps more importantly, Caesar left us the Julian calendar, which he personally introduced during his stint as dictator of Rome in 46 BC. Most of the world now uses a slightly tweaked version of this calendar known as the Gregorian calendar, but some Orthodox churches still use the Julian system in its entirety. Thanks to the tiny mistakes made by Caesar's mathematicians, these churches are now 13 days out of sync with the rest of the world.

From the prestige of the patrician to the degradations of the slave – social status was everything in Rome. Citizenship was a key concept: citizens could own property, marry fellow citizens, rely on legal protections, vote in elections, hold public offices and wear togas. Citizens could also serve in the army as legionaries, who were paid three times as much as the poorly-equipped auxiliary forces. On the bottom rung of Rome’s ladder were enslaved people, who made up 10%-20% of the population and could be legally killed by their masters. Wealthy masters would sometimes free their slaves after years of service (a process known as manumission), which granted them most citizenship rights.

A Roman gladiator had a better chance of surviving a day in the arena than a Roman emperor had of avoiding a violent death. A whopping 62% of emperors met violent ends, some in battle and some by their own hands, but most by the assassin’s blade. Commodus was strangled in his bathtub by a professional wrestler sent by a cabal of disgruntled officials. Geta was murdered while sheltering in his mother’s arms on the orders of his brother Caracalla. And Caracalla was in turn killed by his own bodyguards while relieving himself on the roadside. To modern eyes a lot of Roman emperors seem vicious and paranoid, but they had a lot to be paranoid and vicious about.

Given all this very literal backstabbing, it’s almost surprising that the empire got through the best part of a century before its first major civil war. But AD 69 made up for lost time with a four-emperor bloodbath that called time on Rome’s first dynasty. Veteran senator Galba nabbed the throne after the demise of Nero in AD 68, but was promptly murdered and replaced by Otho the following year. Otho was, in turn, defeated in battle by Vitellius, who was quickly toppled and executed by supporters of Vespasian. Vespasian became AD 69’s fourth emperor when he was recognised by the Senate on 21 December, surviving not only the year’s remaining 10 days but also the next 10 years.

Not to be outdone, the 2nd century brought the Year of Five Emperors (AD 193), in which months of civil bloodshed were again ended by the ascension of a new dynasty. The worst was yet to come, as in AD 235 the empire entered what is known as 'the Third Century Crisis', a 50-year period of invasion and disintegration that brought Rome to its knees. Perhaps inevitably, this period included the Year of Six Emperors (AD 238), whose claimants included a pair of co-emperors with the same name who ruled for 22 days. The exact chronology of the year is still disputed – basically, it was a mess.

With high mortality rates, zero tolerance for female rule and the risk of continent-wide catastrophe accompanying disputed successions, emperors often 'adopted' their chosen heirs as their sons early in the reigns. First emperor Augustus was the adopted son of Julius Caesar, while the list of adopted rulers includes Tiberius, Caligula, Nero, Trajan, Hadrian, Antoninus Pius and Marcus Aurelius (pictured). By the time Marcus Aurelius named his natural-born son Commodus his co-emperor and heir in AD 177, he was practically breaking with tradition. Since Commodus was sufficiently disastrous to play the villain in hit movie Gladiator 1,800 years later, it may have been a mistake.

Rome's imperial throne had some eccentric – to put it kindly – occupants. Nero (AD 54-68) killed his second wife then forced a young boy to dress up in her clothes, while the megalomaniacal Commodus (AD 177-192) entered gladiatorial games dressed as Hercules and briefly renamed Rome after himself. But it's Caligula (AD 37-41) who remains the most notorious crazy emperor, after allegedly executing senators for forgetting his birthday and trying to give his favourite horse a position in the Senate. Modern historians suggest that many of Caligula's misdeeds are later exaggerations, but he was nevertheless bumped off by his own bodyguards after just four years in power.

This may sound unsanitary, but there is a solid scientific basis for this exceedingly gross practice. Roman launderers were known as 'fullers', who would collect – in whatever way they could – the urine of men and animals and mix it with alkali metals and water. They would then scrub the clothes of high-ranking Romans with the mixture, during which the ammonia in the urine would break down dirt and stains. So next time a TV show depicts a stern senator or emperor manoeuvring Rome's legions with a sneer of cold command, remember that his toga has probably been soaked in pee.

These are the most beautiful treasures the Romans left behind

Another bodily fluid fact that’s wheeled out in children’s books to get kids interested in history – this one sadly isn't true. The story goes that Roman elites were so dissolute and debauched that they would stuff themselves at feasts, stumble to a side room (the 'vomitorium') to throw up, and then return with emptier stomachs to continue gorging. Vomitorium is a real Latin word, but it referred to amphitheatre passageways that 'disgorged' spectators to their seats. Romans weren't averse to the odd vomiting session – the emperor Claudius supposedly used a feather in the throat to cure bloating – but, fortunately for domestic servants everywhere, it was not a staple part of evening menus.

The elegant Roman villa, with its colonnades and courtyards, gives an extremely rose-tinted picture of what Roman domestic life was like. Most ordinary Romans lived in squalid tenement blocks known as 'insulae', which were commonly five to seven storeys high and extremely overcrowded. Fire was an ever-present threat – and spelled doom for those on higher levels – while aristocratic landlords rarely lifted a finger to ease conditions. Even the famously upstanding Cicero, one of the great lawyers and statesmen of the late Republic, once joked that even rats would not stay long in his lodgings.

In 1979 comedy Monty Python's Life of Brian, our titular hero is caught scrawling ‘Romans go home’ in Latin on a wall in the forum, only to have his grammar corrected by a passing centurion. The scene is more realistic than you'd think, as graffiti was a common form of expression across the Roman world and often contained spelling errors. In Pompeii alone more than 11,000 examples survive, many of which are too rude to publish, but among the rest are electoral slogans, impromptu poems and notes for loved ones. It wasn't even frowned upon – at least, not by most. One Pompeii epigram reads: "I'm amazed, O wall, that you have not fallen to ruin, you who support the tediousness of so many writers."

The Romans were generally dispassionate towards animals – casually starving them before tossing them into the arena – but at least a few Romans loved their pet dogs dearly, as seen in their funerary epitaphs. "I am in tears," reads one, "while carrying you to your last resting place, as much as I rejoiced when bringing you home 15 years ago." "My eyes were wet with tears, our little dog," reads another, "when I bore you to the grave...never again shall you give me a thousand kisses. Never can you sit contentedly in my lap." Another simply states: "Myia never barked without reason. But now he is silent."

Rome owes its enduring legacy to many things, but chief among them is its own tendency to write down – and sometimes lavishly embellish – its own story. The Romans saw their past as key to their present, and writers like Tacitus (pictured), Suetonius and Cassius Dio penned long, vivid and accurate-ish accounts covering most of Rome's history. Of these three giants, the acerbic and cynical Tacitus stands a cut above, especially his book Annals which covers four of Rome's first five emperors. Enduring Tacitus quotes include "in valour there is hope" and "the more corrupt the state, the more numerous the laws".

These histories often record events that are corroborated by archaeological evidence and other sources, but they are also quick to dramatise and include details their authors could not possibly have known. Suetonius enjoyed giving Roman emperors theatrical last words – "Have I played my part well in the comedy of life?" muses Augustus on his deathbed, while Nero exclaims "Oh, what an artist dies in me!" as assassins close in. "Oh dear, I think I am becoming a God", a deadpan quip attributed to soldier-turned-emperor Vespasian (pictured), fits neatly with his reputation for good humour, but less well with his agonising death from dysentery.

By the 1st century AD, unmarried Roman women could own and inherit property, make contracts and represent themselves in court – freedoms that eluded women in many other societies. But on the occasions that Roman historians mention women at all, they tend to get a pretty raw deal. Messalina and Agrippina the Younger, both key figures in Rome’s first imperial family, were widely smeared as scheming manipulators by day and ludicrously insatiable adulterers by night. Modern historians are kinder, painting both women as formidable operators who carved out behind-the-scenes power bases at a cutthroat court.

Unfortunately almost everything we know about Roman women comes via the quills of Roman men, most of whom were invariably patronising. The poet Ovid described women as primitive and irrational, while the great Republican lawyer Cicero emphasised their "infirmitas consilii" (weak judgement). The satirist Juvenal, meanwhile, was so scathing in his Satire VI that in English it's often titled simply Against Women. Described as "the high point of the misogynistic literature of classical antiquity", the work implores its male readers to avoid marriage at all costs. He's particularly scorching about in-laws: "All chance of domestic harmony is lost while your wife’s mother is living."

If you were a Gaulish slave, criticising Rome was not in your best interests, but for Rome’s historian and philosopher class, it could be something of a hobby. What 'Rome' meant and should mean was a favourite topic for writers like Tacitus, and some of his most famous lines skewered the imperial regime. In recent sword-and-sandals epic Gladiator II, Paul Mescal’s Lucius rails against Rome with the line: "They create desolation and call it peace!" The line comes directly from Tacitus – himself a Roman senator. It’s this penchant for self-reflection that, among other things, helps many Roman texts remain remarkably readable.

There are many differences between Roman society and our own, but how we treat successful actors may be the biggest of them all. Amphitheatres dot Roman ruins even today, and plays both tragic and comic were entertainment staples across the empire. But, despite constant patronage from the Roman elite, actors ranked among the dregs of society – little better than beggars. To give you a sense of their social standing, a law passed by the emperor Augustus in 18 BC forbade free Roman citizens from marrying brothel workers... or actors.

Roman attitudes to sexuality can be difficult for modern observers to get their heads around. The Romans would not, for instance, endorse the distinction between homosexuality and heterosexuality, focusing instead on different sexual roles. And although they were very conservative in their own ways, they were certainly not prudish. Some of the most explicit poetry ever written flowed from the stylus of Catullus – a 1st century BC Roman aristocrat with a colourful private life. It’s so explicit, in fact, that we’re not even going to quote it in Latin.

There’s being sent to bed without your dinner, and then there’s being sold by your parents into a life of brutal and impoverished servitude. In Roman law the 'paterfamilias' (father) had almost complete control over his household – known as the 'patria potestas' (power of a father). This meant he could treat his children as he wished, including selling them to slave dealers if times got tough. Fortunately this was rare, and most patriarchs contented themselves with complaining about young Romans in often familiar terms. "The beardless youth," wrote Horace in the 1st century BC, "does not foresee what is useful, squandering his money."

Many of our enduring images of Rome – legionaries lining up for battle, gladiators clashing in the arena, slaves being whipped by their masters – involve acts of orchestrated violence that shock modern viewers. Particularly shocking was the practice of ‘exposure’, in which unwanted babies would be left in isolated locations to expire. But death was part of life in ancient Rome whether the Romans liked it or not. This was a world in which around half of all children died before their 10th birthday – exposed or otherwise – and deadly plagues spread without cure. Life was certainly cheap, but no cheaper than in many other civilisations before or since.

There's a recurring joke in Roman literature: an elegant dinner party is suddenly invaded by a gaggle of excited 'vigiles' with buckets and axes, who have mistaken smoke from the kitchen chimney for a fire. The vigiles were Rome's – and maybe the world's – first fire brigade, formed by the emperor Augustus in AD 6 following a city-wide blaze. Nicknamed the 'sparteoli' ('little bucket fellows'), they were divided into seven 1,000-strong cohorts in different parts of the city. Full of baker's ovens and sacred flames, Rome experienced 100 fires a day, so you can forgive the vigiles for being a little jumpy. Their day of reckoning came in AD 64, when the Great Fire of Rome levelled two thirds of the capital.

Today the Colosseum is the public face of Roman sport, but in the early centuries AD it was down the road at the Circus Maximus that the real crowds gathered. Up to 250,000 people filled the towering stands to watch four teams of chariot racers – imaginatively named the reds, blues, greens and whites – hurtle round a U-shaped track at breakneck speed. Rivalry between fans could be as heated as at any modern derby, and archaeologists have uncovered 'curse tablets' wishing broken bones on an opposing faction's charioteers. They may well have paid off, as the hairpin bends made crashes and fatalities all too common.

From columns on buildings to major European languages – Rome’s inheritance is inestimable. But many subsequent empires tried to claim its legacy in a more direct way. When the Ottoman Turks completed their conquest of the Eastern Roman Empire in 1453, their leader promptly styled himself Kayser-i Rûm ('Roman Caesar'). The Russian Empire’s first tsars did the same ('tsar' is derived from 'Caesar'), while in Central Europe the Holy Roman Empire was even more literal. Even in modern-day America comment writers muse over whether the US is "the new Rome". The real emperors would, more than likely, think all these candidates unworthy.

Read on to learn about the largest empires in history